Digital Subscriber Line (DSL) technology is widely-used today for increasing the bandwidth of digital data transmissions over the existing telephone network infrastructure. In a typical system configuration, a plurality of DSL subscribers are connected to a service provider (SP) network through a Digital Subscriber Line Access Multiplexer (DSLAM), which concentrates and multiplexes signals at the telephone service provider location to the broader wide area network. Basically, a DSLAM takes connections from many customers or subscribers and aggregates them onto a single, high-capacity connection. The DSLAM may also provide additional functions such as routing or Internet Protocol (IP) address assignment for the subscribers.
Asynchronous Transfer Mode (ATM) protocol networks have traditionally been utilized for communications between DSLAM devices and web feature servers such as Broadband Remote Access Servers (BRAS) and Layer 3 Virtual Private Network (L3VPN) servers. A BRAS is a device that terminates remote users at the corporate network or Internet users at the Internet service provider (ISP) network, and commonly provides firewall, authentication, and routing services for remote users. The ATM protocol is an international standard in which multiple service types (such as voice, video, or data) are conveyed in fixed-length “cells” over point-to-point network connections. ATM networks need a virtual circuit (VC) to be set up across the network before data transfer may occur. That is, communication between a subscriber and a feature server requires allocation of a separate VC. Data packet cells travel through the ATM switches from the user network interface (UNI) to the network node interface (NNI) through a process called Virtual Path Identifier/Virtual Channel Identifier (VPI/VCI) translation. The VPI/VCI identifiers are used by the ATM switches to switch/direct the subscriber traffic to a given feature server, and in the reverse direction to forward server traffic to a given DSLAM/subscriber, without ambiguity. Furthermore, the VPI/VCI mechanism is used by the feature server to identify the subscriber. By way of background, U.S. Pat. No. 6,801,533 teaches a system and method for proxy signaling in a DSLAM and generally describes a DSL network that includes communication transfer of signals from a DSLAM to a remote access server over a high-speed ATM network. Transmission of packet data over an ATM network is also taught in U.S. Pat. No. 6,785,232.
Ethernet is a technology that originated based on the idea of peers on a network sending messages in what was essentially a common wire or channel. Each peer has a globally unique key, known as the Media Access Control (MAC) address to ensure that all systems in an Ethernet have distinct addresses. Most modern Ethernet installations use Ethernet switches (also referred to as “bridges”) to implement an Ethernet “cloud” or “island” that provides connectivity to the attached devices. The switch functions as an intelligent data traffic forwarder in which frames are sent to ports where the destination device is attached. Examples of network switches for use in Ethernet network environments are found in U.S. Pat. Nos. 6,850,542, 6,813,268 and 6,850,521.
As the use of Ethernet has become more widespread, researchers and service providers have developed a variety of methods and systems for data transmission using Ethernet technology. For example, U.S. Pat. No. 6,829,252 teaches a DSLAM device that incorporates a means of transporting Ethernet frame data over a very high-speed DSL (VDSL) transport facility. According to this approach, Ethernet frames are encapsulated within High-Level Data Link Control (HDLC) protocol formatted VDSL frames, which are then transmitted over a plurality of point-to-point links to customer sites. Ethernet-based DSL methods and systems are also described in U.S. Pat. No. 6,785,265.
The proliferation of Ethernet has also led service providers to seek ways of using Ethernet access network technology instead of ATM network technology to connect and aggregate DSLAM traffic to BRAS and other feature servers. However, achieving the three basic requirements of: (1) directing subscriber traffic to a given feature server depending on the requested service; (2) identifying the subscriber at the feature server; and (3) directing feature server traffic to a given subscriber in the reverse direction—all without any ambiguity—has proven difficult.
According to one proposal, Dynamic Host Configuration Protocol (DHCP) relay agents or Point-to-Point over Ethernet (PPPoE) intermediate agents are incorporated into the network edge device, e.g., the DSLAM or Ethernet access switch. (PPPoE is a specification for connecting Ethernet users to the Internet through a common broadband medium such as a DSL.) In this approach, the Ethernet edge device provides the DHCP server or Remote Authentication Dial-In User Service/Authentication, Authorization and Accounting (RADIUS/AAA) server with the same information it would normally receive from a BRAS DHCP relay agent or from a BRAS RADIUS client function in an ATM network. Although this proposal solves the problem of identifying the subscriber at the feature server, it fails to satisfy the other two requirements listed above.
In another proposal, the edge device translates the source MAC address of the subscriber packets into a new MAC address encoded with a DSLAM ID and line ID. This translation is performed such that the resultant MAC address is unique within the service provider network. When the packet is received by the feature server, the subscriber ID is extracted from the source MAC address. This proposal, however, suffers from several drawbacks that include limited DSLAM ID and port ID space, problems with reverse mapping of the provider MAC address to a subscriber MAC address, and security issues. Additionally, this approach is inadequate for multipoint applications where a separate broadcast domain (e.g., separate VLAN) is needed per service instance.
Thus, what is a needed is an alternative system and method for data communications between DSLAM devices and feature servers over an Ethernet network that overcomes the shortcomings of past approaches.